Synthesis of Benzo[c]Selenophenes and Their Analogues: Methods and Advances

The fusion of benzene with selenophene motifs in hybrid configurations yields two distinct structural types: condensed benzo[b]selenophenes and benzo[c]selenophenes. Benzo[c]selenophenes are distinguished by the placement of a selenium atom at the second position rather than the first. To date, no specific studies have focused exclusively on this scaffold, which has been predominantly utilized as a versatile building block in various applications. The synthesis of benzo[c]selenophenes and their analogues can be accomplished through multiple chemical pathways, including (i) selenation reactions using reagents like Woollins' reagent, Na₂Se₂/DMSO, 1,1,1,3,3,3-hexabutyldistannaselenane in toluene, selenium/NMP, and Na₂Se in THF; (ii) Suzuki, Stille, and Sonogashira coupling reactions; (iii) photocyclization reactions; (iv) nucleophilic and metallic substitution reactions; (v) [2 + 2 + n] cycloaddition reactions; and (vi) organometallic reactions, among other methods.